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Viper-56, 4.0HP 220V SD Waterway Spa Pump, 2.5-inch, 3721621-1V


Viper-56, 4.0HP 220V SD Waterway Spa Pump, 2.5-inch, 3721621-1V

Waterway Spa Pump, Viper 56-Frame model, 4.0HP 220V 2-Speed Side Discharge, with 2.5" Intake and 2.5" Discharge. OEM part number 3721621-1V. Model PV-40-2N22C.

SpaGuts P/N: 15-350-1621


  • 220V 60Hz 12.0/4.4A
  • RPM 3450/1725
  • Viper wet end designed specifically for 56-frame motors
  • 2.5" Center Suction, and 2.5" Side Discharge (Outside thread measures approximately 3.6-inch)
  • Dual Speed Pump (can also be wired for single speed)
  • Large 2.5" intake for improved flow performance and reduced noise
  • Large 8" diameter wet end for increased volume capacity
  • 56-Frame Motor for added strength, cooler operating temperature and longer motor life
  • Split Capacitor, (start and run) for less energy consumption
  • Thermally protected to extend life expectancy of motor
  • UL and CUL certifications
  • Equipped with the highest quality Viton Pump Seal
  • Equipped with the high efficiency electrical motor and high performance pump wet end
  • One year manufacturer's limited warranty on motor and wet end

NOTE: Amp rating and dimension may vary slightly depending on the motor brand and model that is used with this pump. Motor brand can be US Motors, AO Smith Century Laser, GE, Etc...

The pump image shows the pump discharge on top pointing to the 12 o'clock position. The pump discharge can also be rotated every 90-degrees (3, 6 or 9 o'clock positions) by loosing the four long bolts at the back of the motor. The pump intake (suction) is located in the front center face of the pump.

If buying this pump for retrofitting, add a pair of pump unions that connects to your pipes which then screws directly onto the pump threaded fittings. O-rings are included with the pump unions.

If buying this pump as an exact replacement that does not require retrofitting, it is highly recommended to replace the pump union o-rings at the same time. Old pump union o-rings may cause leaks that can damage the new pump and affect the warranty. O-rings for pump unions are only available with a pump union purchase.

You may add a cord to be attached to the motor at a discounted price. See cord options below.

The pump normally ships from the factory with the discharge pointing "UP" which is the standard position for shipping, but they can be turned or what is called "clocked" into any position (12, 3, 9 or 6 o'clock position). Rotation of the pump discharge can be done in the field, but we recommend having it performed by a professional spa technician who is experienced. Or choose the option to have the pump professionally rotated at the factory before it ships. This is to avoid water leaks and operational problems due to improper removal and installation in the field that will affect the warranty. As you face the front end of the pump wet end, available positions are 12 o'clock (Up), 3 o'clock (Right), 9 o'clock (Left), and 6 o'clock (Down, which is very rare).

This Viper-56 pump is a replacement option for the following pumps (Just match the amp rating to get the same performance pump): 3721621-1T, 3711621-0T, 5KCP49UN9096XVIPER, 1-00-0106, 3721621-0T7H, PV30-2N22C (Model; Must Verify Pump), 3711621-0T7N (Single Speed),

Keep in mind to not over power your spa by going from a 48-frame motor to a 56-frame motor. Click here to see flow chart, amp rating and dimensions of the Viper pumps.

This pump normally uses the following motor part numbers: 0-187563-02, R63MWENA-4727

The pump wet end will have the model numbers 311-1510 and 315-1500. Make sure to match amp rating.

$584.95 In Stock Viper_Pump_M.png


This item has options that require your selection below. Please make a selection for each option
Hover on Learn More to read about the respective option.
Pump Discharge Orientation Learn More
Up (Standard)
Down (add $9.95)
Left (add $9.95)
Right (add $9.95)
Pump Cord Option Learn More
No Cord
Red JJ Mini Motor Cord 4-Pin 2-Speed 14/4 AWG 4ft (add $12.95)
Pink JJ Mini Motor Cord 3-Pin 1-Speed 14/3 AWG 4ft (add $12.95)
Brown JJ Mini Motor Cord 4-Pin 2-Speed 14/4 AWG 4ft (add $12.95)
Amp Motor Cord 4-Prong 2-Speed 14/4 AWG 4ft (add $12.95)
Amp Motor Cord 4-Prong 1-Speed 14/3 AWG 4ft (add $12.95)
Add 2.5 inch Pump Unions Learn More
No pump unions
Yes, add a pair of 2.5 inch pump unions (add $11.99)